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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, =?UTF-8?q?kiyin ?= <kiyin@tencent.com>,
        Xiaoming Ni <nixiaoming@huawei.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.9 08/47] nfc: Avoid endless loops caused by repeated llcp_sock_connect()
Date:   Thu, 15 Apr 2021 16:47:00 +0200
Message-Id: <20210415144413.747208914@linuxfoundation.org>
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From: Xiaoming Ni <nixiaoming@huawei.com>

commit 4b5db93e7f2afbdfe3b78e37879a85290187e6f1 upstream.

When sock_wait_state() returns -EINPROGRESS, "sk->sk_state" is
 LLCP_CONNECTING. In this case, llcp_sock_connect() is repeatedly invoked,
 nfc_llcp_sock_link() will add sk to local->connecting_sockets twice.
 sk->sk_node->next will point to itself, that will make an endless loop
 and hang-up the system.
To fix it, check whether sk->sk_state is LLCP_CONNECTING in
 llcp_sock_connect() to avoid repeated invoking.

Fixes: b4011239a08e ("NFC: llcp: Fix non blocking sockets connections")
Reported-by: "kiyin(尹亮)" <kiyin@tencent.com>
Link: https://www.openwall.com/lists/oss-security/2020/11/01/1
Cc: <stable@vger.kernel.org> #v3.11
Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/nfc/llcp_sock.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/net/nfc/llcp_sock.c
+++ b/net/nfc/llcp_sock.c
@@ -685,6 +685,10 @@ static int llcp_sock_connect(struct sock
 		ret = -EISCONN;
 		goto error;
 	}
+	if (sk->sk_state == LLCP_CONNECTING) {
+		ret = -EINPROGRESS;
+		goto error;
+	}
 
 	dev = nfc_get_device(addr->dev_idx);
 	if (dev == NULL) {